PHILADELPHIA — Judges have been asked repeatedly to decide whether the lawmakers in charge of drawing congressional district lines have gone too far to favor their parties.

A group of Democratic voters from Pennsylvania is approaching the issue in a different way, asserting it’s wrong for the congressional map to be made to boost one party — at all.

The case is scheduled to be tried starting this week before a three-judge federal panel.

The potential fallout is immense in a state where Republicans have consistently controlled 13 of 18 congressional seats even though statewide votes for congressional candidates are usually divided nearly evenly between Republicans and Democrats. A victory for the plaintiffs could mean a quick redrawing of districts before the 2018 midterm elections and could establish new rules for how congressional districts are remade after the 2020 census.

An appeal of the verdict would go straight to the U.S. Supreme Court, which is already weighing another closely watched partisan gerrymandering case out of Wisconsin.

The Pennsylvania suit is one of three current challenges to the congressional districts Pennsylvania lawmakers approved in 2011. A trial in one of the other cases is scheduled for state court starting Dec. 11.

In all the cases, Democratic voters argue that Republicans who control the Legislature and the redistricting process made maps giving Democrats overwhelming majorities in some areas and then created more districts where Republicans have safe but not overwhelming advantages. Some of them have odd, zigzagging shapes.

The case scheduled for trial in federal court was brought by voters from each of the state’s congressional districts.

The respondents in the lawsuit include the Republican legislative leaders who oversaw the drawing of the map.

In a court filing, lawyers for Mike Turzai, speaker of the state House of Representatives and a Republican candidate for governor in 2018, suggested that part of the defense would be challenging whether the voters have legal standing to bring the lawsuit. They argue that the people who are suing may not be able to show how they were personally harmed by the way the districts were drawn.

The plaintiffs’ claim is based on the part of the U.S. Constitution that gives states the right to set the rules for electing members of Congress but also says Congress can alter those regulations. Other cases over political gerrymandering of districts assert that by drawing boundaries to favor one party too heavily, it dilutes the power of members of the district’s minority party.

In 2004, a divided U.S. Supreme Court decided not to intervene in a political gerrymandering case from Pennsylvania. Justice Anthony Kennedy was the deciding vote, writing that the court could force new lines to be drawn “if some limited and precise rationale were found to correct an established violation of the Constitution in some redistricting cases.”

Alice Ballard, a lawyer for the plaintiffs in the new suit, says her case finds a way to determine find a clear way to do that. Other cases, she said, are “about trying to come up with the line between the ‘some’ that’s tolerable and the ‘too much’ that’s not tolerable. Our standard is: No partisan gerrymandering, period.”

The lawsuit was filed only in October, but it has been full of contention, with about 40 lawyers involved.

They have argued over when and how long the plaintiffs could be questioned by opposing lawyers and whether lawmakers could be forced to hand over any communications they had during their mapmaking with national Republican groups.

Turzai even asked if he could give a deposition that would not be made public in the future. A judge rejected the request.